Clamping chucks of this kind are known, for example, from DE 38 22 506 C1, and in practice are used chiefly to clamp workpieces onto lathes for machining. Conventional clamping chucks are embodied in the manner of a three-jaw chuck, and possess three clamping jaws that are arranged in corresponding radial jaw guides of the chuck body. Guidance of the clamping jaws in the jaw guides is accomplished via corresponding guide grooves and guide rails that are embodied on the lateral surfaces of the clamping jaws and of the jaw guides.
One problem that often occurs in conventional clamping chucks is that with increasing circumferential velocity, large centrifugal forces occur which cause the inherently preloaded clamping jaws to be pulled outward, thus resulting in a decrease in clamping force. For this reason, in the clamping chuck previously known from DE 38 22 506 C1, a centrifugal force compensation is effected by way of centrifugal force compensation weights that are each arranged shiftably below an associated clamping jaw in the chuck body, and are connected to the clamping jaw via a clamping lever that is braced in pivotably movable fashion in the chuck body and rests with its one end in a guide recess of the compensation weight, and with its second end in a guide recess of the clamping jaw. Upon the occurrence of centrifugal forces, the clamping lever is pulled outward by the compensation weight and simultaneously transfers a force counteracting the centrifugal force of the compensation weight to the clamping jaw, which consequently is retightened.
In the known clamping chuck, the radial motions that the centrifugal force compensation weights execute upon a shifting of the clamping jaws are furthermore used to pump lubricating grease, which is displaced out of the jaw guides during operation by the resulting centrifugal forces and collects in the pockets of the centrifugal force compensation weights, back into the region of the jaw guides. Embodied for this purpose on the underside of the centrifugal force compensation weights, in the levers, and in the clamping jaws are lubricant conduits through which the lubricant that collects in the radially outer region of the pockets is pushed into the region of the sliding surfaces between the clamping jaws and the chuck piston when the centrifugal force compensation weights are shifted radially outward upon a radially inward shifting of the clamping jaws and the radially outer region of the pockets thus becomes smaller.
A disadvantage of this known approach is that the pumping action resulting from the motion of the centrifugal force compensation weights is not sufficient if the pockets are only partly filled with lubricating grease; and the risk also exists that some of the lubricant contained in the lubricant conduits will be aspirated back into the pocket in the context of an inwardly-directed motion of the centrifugal force compensation weights.